The present invention relates generally to method and apparatus for manufacturing a wood blind, and more particularly a method and apparatus for punching edge notches in a wood slat for a light blocking blind.
Venetian blinds include a plurality of slats connected together with at least two ladder cords that sets the spacing of the lift cords and controls the tilting of the slats, from an open to a closed position. Additionally, a venetian blind includes at least two of lift cords that extend through respective lift cord holes in each slat and are attached to a bottom member. The lift cords act to raise and lower the bottom member and the plurality of slats. Typically, the lift cord holes are located halfway between the longitudinal edges of each slat. Since the holes are larger in diameter than the lift cords, light is able to pass through the holes when the blind is in the closed position.
When the slats are in the closed position, each slat overlaps the edge of an adjacent slat. By placing the lift cord holes on the edge of the slats, it is possible to eliminate light from passing through the lift cord holes when the blind is in the closed position. However, this typically requires that a lift cord be placed on either side of the wood slat to ensure that the slats are maintained in a horizontal orientation when the blind is raised. In order to enhance the aesthetic view of the blind, the lift cord pair located on both sides of the slat are in alignment. Therefore, the location of the lift cord holes must also be in alignment.
A number of automated processes have been developed to form a venetian blind from a continuous roll of aluminum slat material. For example U.S. Pat. No. 5,243,744 discloses a machine for producing venetian blinds including a punching device for punching a lift cord hole in an aluminum slat. Unlike, aluminum, wood slats are not produced from a continuous roll of material, But rather are processed as individual strips. While, lift cord holes have been punched in the center of wood slats utilizing a shear punch, this has not proven effective for forming the through holes or notches on the edge of the wood slats. The shear punch works to punch a hole in the center of a wood slat where there is sufficient slat support around the hole. However, utilizing a traditional shear punch on the edge of the slat results in striping or cracking of the slat.
In order to overcome this problem of cracking the slat when forming a notch or hole on the edge of a slat, a router is used to rout the edge notches or by using a saw blade by making a plurality of cuts. However the use of a router or saw, typically requires that each notch be formed independently. Due to lag in the position of automated router equipment, and imprecise positioning of cutting equipment, the notches are subject to being improperly aligned. As a result the lift cord pairs are out of alignment resulting in less aesthetically pleasing blinds. It would therefore, be desirable to form the edge notches in wood slats in a way that minimizes misalignment. Further, it would be desirable to have the benefit of punching an edge notch on a wood slat without cracking or stripping the wood. It would also be desirable to form pairs of notches simultaneously to increase the speed of production.
Accordingly, a method and apparatus for punching edge notches in a wood slat is provided in which each pair of edge notches is formed simultaneously with a single die to ensure alignment of the edge notches.
According to one exemplary embodiment an apparatus for forming a notch on the edge of a wood slat includes a punch assembly having a die plate, a stripper and a first punch. The die plate includes a support surface to support the bottom surface of the wood slat, and a guide to locate a longitudinal edge of the wood slat. The stripper is movable relative to the wood slat for engagement and disengagement of the top surface of the wood slat. The first punch is movable relative to the wood slat for punching a notch on one longitudinal edge of the wood slat.
In accordance with an exemplary method for forming a notch on an edge of a wood slat, the wood slat is fed to a punching station. The lower surface of the wood slat is located on a die plate. The longitudinal edge of the wood slat is located within a punching station. The wood slat is also located with a stop along a leading edge of the wood slat. A stripper is biased against the upper surface of the wood slat. The edges of the wood slat are punched with a pair of punches. Each punch has a beveled region to form a notch on one of the respective edges of the wood slat.
In accordance with another method for forming a notch on an edge of a slat having a predetermined length, the slat is fed to a punching station. The slat is located within the punching station along a longitudinal edge. The slat is moved along its longitudinal axis to a stop at a predetermined location relative to the punching station. A stripper plate contacts the upper surface of the slat. The slat is punched with a pair of punches to form a notch on each of the respective edges of the slat.
The punch utilized for forming the notches on the slats may include a beveled region having a v-shaped cutout.